Safranal

Safranal has the systematic name 2,6,6-trimethylcyclohexa-1,3-diene-1-carbaldehyde and the formula C₁₀H₁₄O. Its molecular weight is 150.22. It is an aldehyde monoterpene and the volatile component responsible for saffron essential oil. It is believed to be a degradation product of the carotenoid zeaxanthin via the intermediate picrocrocin. The compound is isolated from saffron, the spice consisting of the stigmas of Crocus sativus flowers. It is insoluble in water and soluble in oils; it mixes with ethanol at room temperature and dissolves in methanol, petroleum ether and glacial acetic acid.

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Safranal in Saffron

Safranal is a volatile oil that gives saffron much of its distinctive aroma. Crocin, picrocrocin and safranal are the main compounds of saffron and account for its colour, taste and odour respectively. Safranal is the most abundant chemical in saffron essential oil and accounts for 60-70% of the volatile fraction. Good-quality saffron holds about 2.5% volatile compounds such as safranal. Saffron contains some 28 volatile and aroma-yielding compounds, dominated by ketones and aldehydes. Its main aroma-active compounds are safranal, 4-ketoisophorone, and dihydrooxophorone. Chemists find that 2-hydroxy-4,4,6-trimethyl-2,5-cyclohexadien-1-one is the most powerful contributor to saffron's fragrance, despite its presence in a lesser quantity than safranal. That molecule smells of saffron and dried hay. The aroma compounds of saffron fall into three groups: mono- and sesquiterpenes from the isoprenoid pathway, phenylpropanoids and benzenoids from the shikimic acid pathway, and compounds from the enzymatic conversion of lipids by β-oxidation. Geographical origin makes a great difference in the safranal content of saffron. A gas chromatography study of Iranian saffron found 77 volatile compounds, with safranal among eleven biomarkers. Iranian and Moroccan saffron are marked by high levels of acetic acid, isophorone and dihydrooxophorone, whereas Spanish and Greek saffron contain little or no acetic acid.

Relation to Picrocrocin

Picrocrocin is a union of an aldehyde sub-molecule known as safranal and a carbohydrate. Picrocrocin is a colorless and odorless glycoside monoterpene. Safranal is less bitter than picrocrocin. Picrocrocin has the formula C₁₆H₂₆O₇ and the systematic name 4-(β-D-glucopyranosyloxy)-2,6,6-trimethylcyclohex-1-ene-1-carbaldehyde. It is the glycoside of the terpene aldehyde safranal and a truncated form of zeaxanthin produced by oxidative cleavage. Its sugar-free part is 4-hydroxy-2,6,6-trimethyl-1-cyclohexene-1-carboxaldehyde, also called hydroxy-β-cyclocitral or HTCC. Picrocrocin gives saffron its bitter taste and is the second most abundant component of its dry matter. Fresh samples are more bitter, because during storage picrocrocin loses its sugar residues and becomes HTCC and safranal.

Stability and Supply

Dry saffron is highly sensitive to fluctuating pH levels, and rapidly breaks down chemically in the presence of light and oxidising agents. It must be stored in airtight containers to limit contact with atmospheric oxygen, and it resists heat somewhat better. Temperature and humidity strongly affect how fast the main active ingredients degrade. Merchants allow a shelf life of three to four years when saffron is kept at room temperature away from light. Saffron processed and stored under optimal conditions keeps its organoleptic characteristics for one to four years. Saffron is the commercial name for the dried red stigmas of Crocus sativus. Approximately 150,000 flowers must be collected to produce 1 kg of saffron. Collecting 1000 flowers takes about 45-55 minutes and removing their stigmas for drying another 100-130 minutes, so 1 kg of dry stigmas costs 370-470 hours of work. Saffron is considered a high-priced condiment (1500-2200 euro/kg) because of the considerable labor involved in its production. World production is approximately 430 tons of saffron a year.

Biological Activity

Safranal is an effective anticonvulsant in animal models. In those models it acts as an agonist at GABA A receptors. It exhibits high antioxidant activity and, in vitro, cytotoxicity towards cancer cells. One of its anticancer mechanisms disrupts the normal assembly dynamics of cellular microtubules. It has also shown antidepressant properties in animals and in pilot studies in humans. In guinea pigs exposed to a citric acid aerosol, safranal significantly reduced the number of coughs.

Other Natural Sources

Beyond saffron, safranal has been reported in rooibos, tea leaf, fig leaf, wolfberry, cumin seed, elderberry and lemon.